Orbital’s Next Generation Launcher is based on the solid-rocket strap-on boosters that flew on NASA’s space shuttles, Orbital Business Development Director John Steinmeyer said at the 2016 Space Congress conference in Cape Canaveral.

The company plans to buy the rocket’s second stage from Jeff Bezos’ space company, Blue Origin.

Currently, United Launch Alliance—a partnership of Lockheed Martin (LMT) and Boeing (BA)—and Musk’s SpaceX (SPACEX) are the only companies certified to launch U.S. military and national security satellites.

“We’re working cooperatively with the Air Force to make sure there’s room for three players,” Steinmeyer said in an interview with Reuters.

Orbital would launch the rocket from one of the space shuttle’s old launchpads at the Kennedy Space Center in Florida.

If the Air Force maintained requirements for a West Coast launch site as well, Orbital could refurbish a pad at Vandenberg Air Force Base in California, Steinmeyer said.

Orbital in January won an Air Force contract worth up to $180 million to develop rocket propulsion technologies. Steinmeyer declined to say how much Orbital was investing in the project.

Orbital, meanwhile, is preparing to return its refurbished Antares rocket to flight, following a launch accident in October 2014 that destroyed a cargo ship bound for the International Space Station.

The rocket, which has been outfitted with new engines, is scheduled for a test firing at the Wallops Flight Facility in Virginia on May 31, Steinmeyer said. The rocket is scheduled to fly in early July to deliver another cargo capsule to the station for NASA.